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Hook implementations and hook lookup fixes #45

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Dec 17, 2024
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Hook implementations and hook lookup fixes #45

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d91a531
Add hook implementations
virgil-serbanuta Dec 16, 2024
4106356
Use WasmString for function names
virgil-serbanuta Dec 16, 2024
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94 changes: 88 additions & 6 deletions pykwasm/src/pykwasm/kdist/wasm-semantics/ulm-wasm.md
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Original file line number Diff line number Diff line change
Expand Up @@ -83,30 +83,112 @@ infer that this must be the top configuration, so it will wrap it in
A special configuration cell is added in the local case to support VM initialization.

```local
<entry> $ENTRY:String </entry>
<entry> $ENTRY:WasmString </entry>
```


```k
</ulmWasm>
```

Implementing all unresolved imports as hooks
--------------------------------------------

```k

syntax String ::= wasmString2StringStripped ( WasmString ) [function]
| #stripQuotes ( String ) [function]
// ----------------------------------------------------
rule wasmString2StringStripped(WS) => #stripQuotes(#parseWasmString(WS))

rule #stripQuotes(S) => replaceAll(S, "\"", "")

syntax IdentifierToken ::= String2Identifier(String) [function, total, hook(STRING.string2token)]

```

First, we create an empty module for any import referencing a non-existing module.

```k

rule
<instrs> #import(MOD, _, _) ... </instrs>
<moduleRegistry> MR:Map => MR [ MOD <- NEXT ] </moduleRegistry>
<nextModuleIdx> NEXT => NEXT +Int 1 </nextModuleIdx>
<moduleInstances> ( .Bag => <moduleInst> <modIdx> NEXT </modIdx> ... </moduleInst>) ... </moduleInstances>
requires notBool MOD in_keys(MR)

```

Next, for each import referencing a non-existing function, we add a function
that just invokes a (non-wasm) `hostCall` instruction.

```k

syntax Instr ::= hostCall(String, String, FuncType)
// ---------------------------------------------------
rule
<instrs>
( .K
=> allocfunc
( HOSTMOD, NEXTADDR, TYPE, [ .ValTypes ]
, hostCall
( wasmString2StringStripped(MOD)
, wasmString2StringStripped(NAME)
, TYPE
)
.Instrs
, #meta
(... id: String2Identifier
( "$auto-alloc:"
+String #parseWasmString(MOD)
+String ":"
+String #parseWasmString(NAME)
)
, localIds: .Map
)
)
)
~> #import(MOD, NAME, #funcDesc(... type: TIDX))
...
</instrs>
<curModIdx> CUR </curModIdx>
<moduleInst>
<modIdx> CUR </modIdx>
<types> ... TIDX |-> TYPE ... </types>
...
</moduleInst>
<nextFuncAddr> NEXTADDR => NEXTADDR +Int 1 </nextFuncAddr>
<moduleRegistry> ... MOD |-> HOSTMOD ... </moduleRegistry>
<moduleInst>
<modIdx> HOSTMOD </modIdx>
<exports> EXPORTS => EXPORTS [NAME <- NEXTFUNC ] </exports>
<funcAddrs> FS => setExtend(FS, NEXTFUNC, NEXTADDR, -1) </funcAddrs>
<nextFuncIdx> NEXTFUNC => NEXTFUNC +Int 1 </nextFuncIdx>
<nextTypeIdx> NEXTTYPE => NEXTTYPE +Int 1 </nextTypeIdx>
<types> TYPES => TYPES [ NEXTTYPE <- TYPE ] </types>
...
</moduleInst>
requires notBool NAME in_keys(EXPORTS)

```

Obtaining the Entrypoint
------------------------

In the standalone semantics, the Wasm VM obtains an entrypoint from the configuration.

```local
syntax String ::= #getEntryPoint() [function, total]
syntax WasmString ::= #getEntryPoint() [function, total]
rule #getEntryPoint() => FUNCNAME
[[ <entry> FUNCNAME </entry> ]]
```

In the remote semantics, the Wasm VM has a fixed entrypoint.

```remote
syntax String ::= #getEntryPoint() [function, total]
rule #getEntryPoint() => "ulmDispatchCaller"
syntax WasmString ::= #getEntryPoint() [function, total]
rule #getEntryPoint() => #token("\"ulmDispatchCaller\"", "WasmStringToken")
```

Passing Control
Expand All @@ -123,8 +205,8 @@ Note that entrypoint resolution must occur _after_ the Wasm module has been load
This is ensured by requiring that the `<instrs>` cell is empty during resolution.

```k
syntax Initializer ::= #resolveCurModuleFuncExport(String)
| #resolveModuleFuncExport(Int, String)
syntax Initializer ::= #resolveCurModuleFuncExport(WasmString)
| #resolveModuleFuncExport(Int, WasmString)
| #resolveFunc(Int, ListInt)
// ----------------------------------------------
rule <k> #resolveCurModuleFuncExport(FUNCNAME) => #resolveModuleFuncExport(MODIDX, FUNCNAME) </k>
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